The present invention relates generally to a workpiece clamp for a sewing device for clampingly receiving workpiece layers to be stitched together at their margins and, in particular, to a workpiece clamp for sewing a tip area of a necktie.
From a brochure (AMF, Inc., Model 84-23 TT) such a workpiece clamp to be used in a sewing device is known. It is essentially composed of clamping plates hingedly connected with each other.
For sewing the tip of a necktie, at first a lining cut is positioned on a supporting plate and clamped thereto by means of an intermediate clamping plate lowered upon the supporting plate. Subsequently, the tip area of the necktie cut is positioned on the intermediate clamping plate and clamped thereto by means of an upper clamping plate lowered upon the intermediate clamping plate.
A special feature of this workpiece clamp is a folding sword arranged along the symmetry of the intermediate clamping plate. The necktie cut is folded about this sword when the upper clamping plate is lowered upon the intermediate clamping plate, thus forming a center fold. A further special feature are webs formed at the intermediate clamping plate for producing folds in order to meet the material fullness in this area. Besides the formation of the aforesaid three folds, at the marginal zones of the necktie cut to be sewn to the lining cut, there is produced an additional material fullness due to the thickness of the intermediate clamping plate.
After clamping of the lining cut and the necktie cut, and forming the aforesaid material fullness, both workpiece cuts are sewn together at their marginal zones. For this purpose, the sewing device includes guiding means in order to control a relative movement between the workpiece clamp and the sewing machine, according to the profile of the seam to be produced.
During the sewing operation, at first one lateral corner is reached, at which the fullness fold located in this area of the necktie cut is folded down by the seam and into the direction of the seam. In the area of the tip where the center fold ends, there is an automatically controlled interruption of the seam. Subsequently, a new seam is started for sewing the marginal zones of the workpiece cuts. As soon as the second lateral corner is reached, the fullness fold located in this area of the necktie cut is folded down by the seam and also in the direction of the seam generation. Finally, the seam is completed along the remaining shank.
By the afore-described sewing operation, the folds at the lateral corners are folded down and sewn in sewing direction, i.e. in different directions with respect to the necktie itself. When turning these areas of the necktie, the different sewing of the lateral fullness folds causes unequal conditions, which influence the appearance of the necktie and which renders difficult the production of a parallelly extending profile of the lining cut sewn to the necktie cut. These difficulties especially may occur if the texture of the materials to be sewn differs considerably.